Use the heat method if the stickers are not clear coated and just peel them off. The "Oops" product does work well or find some adhesive remove at a local fabric of hobby store. Once you remove all the sticky wipe with water and then give it a good waxing with car wax and you'll never know they were there.
If not too much sticky is left after removing the stickers, most liquid car waxes will remove the sticky film with some rubbing and it will not harm the finish. Besides, waxing the frame makes clean up easy and helps keep your ride looking good.
I just bought a new bike last week.The frame size sticker and a warning sticker near the seat post were on their hard as nails. I couldn't even get my fingernail to lift a corner. A few seconds with a hair dryer and they were nice and soft. They peeled off like putty.